The world of integrated circuits has seen explosive growth and innovation since its inception. Integrated circuits are typically silicon wafers doped in such a manner as to create semiconductor devices thereon, although other permutations such as Gallium Arsenide integrated circuits do exist. The integrated circuits are mounted on printed circuit boards and connected to traces so that the components within the integrated circuit may be used. As the integrated circuit industry has matured and transistor size has decreased, integrated circuits have become more complex and able to do more things while taking up less space.
Integrated circuits are now used for any number of components within myriad devices. For example, televisions, stereos, computers, and the like all use integrated circuits in transmitters, modems, signal processors, and the like. Integrated circuits, despite their power and versatility, are relatively fragile. Specifically, if the integrated circuit receives an input signal with a power level that exceeds the integrated circuit's tolerances, the integrated circuit may be damaged or destroyed.
To minimize the risk of exposing an integrated circuit to excessively powerful input signals, most circuit designers use attenuation circuits composed of resistive components to attenuate input signals to a desired, tolerable level. These attenuation circuits are typically positioned proximate the integrated circuits, albeit off chip, on the printed circuit board within the device that uses the integrated circuit.
In most instances, the existence of off chip attenuation circuits is not unduly burdensome. However, for the class of electronic products known generally as mobile terminals and including cellular phones, laptop computers, personal digital assistants, pagers, and the like, where space within the device is a premium, the existence of off chip components can be a severe design strain. Further, some mobile terminals operate in two or more frequency band modes. It is not uncommon to have different power level tolerances based on the frequency band mode in which the device is operating. Thus, the number of attenuation circuits may double or triple in such multimode devices. As already noted, because space within mobile terminals is a premium and because increased component counts increase costs, it is desirable to have an alternate technique by which attenuation circuits could be provided for use in mobile terminals.